1. Technical Field
This disclosure generally relates to a piezoelectric actuator and a manufacturing method thereof, a liquid ejecting head, and an image forming apparatus.
2. Description of the Related Art
Generally, in a printer, a facsimile, a copier, and an image forming apparatus having the above multiple functions, a liquid ejecting head ejects liquid (ink) droplets of recording liquid, adheres the recording liquid on a recording medium which is carried, and an image is formed on the recording medium.
In this case, the image forming apparatus includes an image recording apparatus, an image printing apparatus, a character writing apparatus, and so on; and forms an image on a recording medium formed of materials such as paper, cloth, leather, metal, glass, plastic, wood, ceramics, and so on. In the image forming, in addition to forming characters and pictures on the recording medium, pattern forming and so on are included.
As the liquid ejecting head, a piezoelectric type head which uses a piezoelectric actuator is well known. In the piezoelectric actuator, a piezoelectric element is used as a pressure generating unit which generates pressure to apply liquid (ink) in a liquid chamber, especially, a stacked type piezoelectric element in which piezoelectric layers and electrode layers are alternately stacked is used, and an elastically deformable vibration plate of which a wall of the liquid chamber is formed is deformed by displacement in the d33 direction or the d31 direction of the stacked type piezoelectric element. With this, the liquid ejecting head ejects liquid droplets by a change of the volume/the pressure of the liquid chamber caused by the deformation of the vibration plate.
In Patent Document 1, an inkjet head is disclosed. In the inkjet head, piezoelectric layers and internal electrodes are alternately stacked, and an individual side external electrode is formed at one side of the stacked body and a common side external electrode is formed at the other side of the stacked body; with this, a stacked type piezoelectric element (driving element block) is formed. By applying a groove forming process to the main part of the driving element block, plural drive sections (driving channels) are formed at the main part and non-drive sections are formed one at each side. Pressure is applied to liquid in a liquid chamber by using displacement in the d31 direction of the stacked type piezoelectric element and the common side external electrodes are disposed at the non-driving sections positioned at both ends in the arraying direction of the stacked type piezoelectric elements.
In Patent Document 2, a stacked type piezoelectric element using displacement in the d33 direction is disclosed. In the stacked type piezoelectric element, a groove forming process is applied to a piezoelectric element formed on a base plate and piezoelectric elements connecting to corresponding liquid chambers having a nozzle are formed.
In Patent Document 3, a line type inkjet head is disclosed. In the line type inkjet head, plural nozzle openings are arrayed on one nozzle plate, a piezoelectric element is disposed at each nozzle opening by processing plural bulk type piezoelectric elements, and a boundary between two adjacent bulk type piezoelectric elements is a part in which a gap is formed therebetween.
In Patent Document 4, a manufacturing method of an inkjet head is disclosed. In the inkjet head, plural liquid ejecting heads are connected.
[Patent Document 1] Japanese Laid-Open Patent Application No. 8-142325
[Patent Document 2] Japanese Laid-Open Patent Application No. 2003-250281
[Patent Document 3] Japanese Patent No. 3156411
[Patent Document 4] Japanese Laid-Open Patent Application No. 2000-351217
However, recently, an image forming apparatus (for example, an inkjet recording apparatus) has been required to perform high-speed printing. In order to satisfy the high-speed printing requirement, the liquid droplet ejecting frequency must be high or the number of nozzles must be large. When the liquid droplet ejecting frequency is high, a carriage for carrying the recording head must be moved at high speed, and a high power motor of the carriage must be accurately controlled. Consequently, in order to execute a stable ejection of liquid droplets at high frequency, the cost of the apparatus is increased.
When a long-length recording head is used for increasing the number of nozzles in the recording head having the piezoelectric actuator in Patent Documents 1 and 2, all the elements in the recording head must be long. Especially, a PZT (piezoelectric transducer) which is a typical piezoelectric element is a very thin and long component; therefore, it is very difficult to manufacture and handle a much longer PZT.
In addition, in the line type inkjet head in Patent Document 3, the piezoelectric element is formed by dividing the bulk type piezoelectric element; therefore, chipping and failing of the piezoelectric element is likely to occur. Consequently, the yield is decreased and the cost is increased.
In addition, in Patent Document 4, since the plural liquid ejecting heads are connected, the size of the recording head becomes large; consequently, the size of the apparatus becomes large.